One of the advantages of a flexible-fuel or a multi-fuel engine is the ability to run on different fuels having different calorific values. Sometimes, two miscible fuels, mixed in a certain volume ratio, may be stored in one fuel tank. At other times, if the two fuels are non-miscible, two fuel tanks may be used. In the operation of a multi-fuel diesel cycle engine, the characteristics of the fuel entering the combustion chambers may change rapidly due to incomplete mixing of the two fuels, such as methanol and diesel fuel. This may occur due to phase separation of the two partially miscible fuels in a single fuel tank, especially if the vehicle has been stationary for a long time. At other times, the characteristics of the fuel entering the combustion chambers may change drastically, during the transition from one type of fuel to another. When this happens, the engine performance suffers, usually evidenced by a transient loss in power. To overcome these inherent problems, one well known solution is to identify the fuel being used by a sensor, and appropriately change the flow rate of the fuel entering the combustion chambers and the injection timing, or the ignition timing of the engine. However, this requires the use of very fast acting sensors and pumps to respectfully sense and respond to the changing fuel characteristics and may not work as well.
It is desirable to have a fuel storage and feeding system having only one fuel tank capable of handling multiple non-miscible fuels for a multi-fuel engine. It is also desirable that these multiple fuels be simultaneously withdrawn and delivered to the engine in a constant volumetric ratio. It is further desirable to provide a smooth transition from one depleted fuel to another available fuel, without causing any sudden change in the engine performance, even though each fuel may have a different calorific value. Further, the fuel storage and delivery system should be economical. The present invention is directed to overcome one or more of the problems as set forth above.